1. Field of the Invention
The present invention relates to a method of fabricating a carbon monoxide detector and a carbon monoxide detector fabricated using the same. The present invention particularly relates to a method of fabricating a carbon monoxide detector, which can be provided under room temperature, operated under room temperature, and having optimum sensitizing selectivity.
2. Description of Related Art
In the present surrounding environment, carbon monoxide is often produced as exhaust gas from cars, factory flues, coal, or fuel gas. When an excessive amount of carbon monoxide is inhaled into a human body, it will decrease the oxygen carrying efficiency of hemoglobin. When a human body is exposed to a high concentration of carbon monoxide situation, the cerebrum will lose its normal function and even death may follow. Furthermore, since carbon monoxide possesses the characteristics of lacking color, taste, and stimulus, people cannot detect any danger through their own senses Therefore, the detection technology of the carbon monoxide detector is particularly important in the present living environment.
The present use of carbon monoxide detectors can be classified into the solid semiconductor type, optical type, electrochemical type, and any other types depending on other principles. The solid semiconductor type carbon monoxide detector detects the presence of carbon monoxide by using a metal oxide semiconductor material, such as indium oxide (In2O3), tin dioxide (SnO2), zinc oxide (ZnO), ferric oxide (Fe3O4), tungstic oxide (WO3), etc. Therefore, when other gases appear in the same space, the detecting ability of these solid semiconductor type carbon monoxide detectors is impaired, and this causes low selectivity and stability, which may be large improved. Besides, these solid semiconductor type carbon monoxide detectors need high operation temperature, such as 200 to 400° C., to be able to work, and all they need high temperature processes for fabrication. Therefore, there are many limits in the providing and using of these solid semiconductor type carbon monoxide detectors.
FIG. 1 illustrates a conventional carbon monoxide detector 1 comprising a substrate 11 having an upper surface 111, which is an aluminum oxide substrate, i.e. a ceramics substrate. A first comb-shaped electrode 121, a second comb-shaped electrode 122, a first pad 123 and a second pad 124 are on the upper surface 111 of substrate 11, wherein the first comb-shaped electrode 121 and the second comb-shaped electrode 122 cross each other in a non-contacting manner, each have one side connecting to the first pad 123 and the second pad 124 respectively, forming two independent electrodes. Furthermore, the first comb-shaped electrode 121 and the second comb-shaped electrode 122 are covered by a tin dioxide layer 13, and the tin dioxide layer 13 is also formed on the upper surface 111 of substrate 11 between the first comb-shaped electrode 121 and the second comb-shaped electrode 122.
FIG. 2A and FIG. 2B illustrate the resistance measured when a carbon monoxide detector of the prior art is applied in carbon monoxide detecting, the difference is that the vapor pressure of oxygen and tetramethyltin in the reacting chamber (not shown) of plasma-enhanced deposition machine (not shown) is 20 mtorr in FIG. 2A when forming the tin dioxide layer of carbon monoxide detector known in the prior art, and the vapor pressure of oxygen and tetramethyltin in the reacting chamber (not shown) of plasma-enhanced deposition machine (not shown) is 40 mtorr in FIG. 2B when forming the tin dioxide layer of carbon monoxide detector known in the prior art.
As shown in FIG. 2A and FIG. 2B, no matter which kind of carbon monoxide detector of the prior art is placed in a detecting chamber (the carbon monoxide concentration in chamber is 400 ppm), when the resistances are measured, all data obtained are unreliable and the detectors cannot be used to detect carbon monoxide.
Therefore, there is a commercial need for a method to provide a carbon monoxide detector at room temperature, and the carbon monoxide detector (provided using the same) can detect at room temperature and possess higher selectivity.